Whole-cell recordings from visualized C1 adrenergic bulbospinal neurons: ionic mechanisms underlying vasomotor tone

Kangrga, Ivan; Loewy, A.

doi:10.1016/0006-8993(94)01282-m

Cited by 63 publications

(54 citation statements)

References 52 publications

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“…During hyperpolarization below the threshold for action potential generation, EPSPs were not observed, and the R firing pattern resumed after release of activity suppression at the end of a hyperpolarizing pulse. The presence of this type of neuron in the RVLM of the in vitro slice preparation has been reported by other investigators (Kangrga and Loewy 1995;Lewis and Coote 1993;Sun et al 1988b). It was also found that the regular firing of some of these neurons was not dependent on synaptic inputs, since it persisted after low-Ca 2ϩ /high-Mg 2ϩ application, in both the slice preparation (Sun and Reis 1994) and in the brain stem/spinal cord preparation (Oshima et al 2000).…”

Section: Types Of Neuronal Dischargesupporting

confidence: 78%

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Rhythmic Properties of Neurons in the Rostral Ventrolateral Medulla of the Rat In Vitro: Effects of Clonidine

Granata¹,

Cohen

2002

Journal of Neurophysiology

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Section: Types Of Neuronal Dischargesupporting

confidence: 78%

“…In addition, similar unitary rhythms have been found in in vitro preparations, such as brain-stem/spinal cord preparations (Oshima et al 2000) and the medullary slice preparation (Granata 1995;Kangrga and Loewy 1995;Lewis and Coote 1993;Piguet and Schlichter 1998;Sun and Reis 1994;Sun et al 1988b).…”

Section: Types Of Neuronal Dischargesupporting

confidence: 53%

Rhythmic Properties of Neurons in the Rostral Ventrolateral Medulla of the Rat In Vitro: Effects of Clonidine

Granata¹,

Cohen

2002

Journal of Neurophysiology

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“…1, A and B). The membrane properties of RVL bulbospinal neurons have been studied in detail elsewhere (Hayar and Guyenet 1998;Kangrga and Loewy 1995;Li et al 1995). The recorded neurons were labeled with Lucifer yellow (Fig.…”

Section: R E S U L T Smentioning

confidence: 99%

“…This method allowed us to restrict our recordings to a population of RVL neurons that consists predominantly of presympathetic neurons (Li et al 1995) and is therefore of special relevance to understanding the central sympatholytic effects of moxonidine. In some experiments, we further characterized whether the recorded neurons could be classified as C1 neurons using immunostaining for tyrosine hydroxylase (Kangrga and Loewy 1995;Li et al 1995). …”

mentioning

confidence: 99%

Prototypical Imidazoline-1 Receptor Ligand Moxonidine Activates Alpha2-Adrenoceptors in Bulbospinal Neurons of the RVL

Hayar

Guyenet

2000

Journal of Neurophysiology

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Hayar, Abdallah and Patrice G. Guyenet. Prototypical imidazoline-1 receptor ligand moxonidine activates alpha2-adrenoceptors in bulbospinal neurons of the RVL. J. Neurophysiol. 83: 766 -776, 2000. Moxonidine is an antihypertensive drug that lowers sympathetic vasomotor tone by stimulating either alpha2-adrenergic (␣2-AR) or imidazoline I1 receptors within the rostral ventrolateral medulla (RVL). In this study, we investigated the effects of moxonidine (10 M) on RVL neurons in brain stem slices of neonatal rats. We recorded mainly from retrogradely labeled RVL bulbospinal neurons (putative presympathetic neurons) except for some extracellular recordings. Prazosin was used to block alpha1-adrenoceptors. Moxonidine inhibited the extracellularly recorded discharges of all spontaneously active RVL neurons tested (bulbospinal and unidentified). This effect was reversed or blocked by the selective ␣2-AR antagonist SKF 86466 (10 M). In contrast, the I1 imidazoline ligand AGN 192403 (10 M) had no effect on the spontaneous activity. In whole cell recordings (holding potential Ϫ70 mV), moxonidine produced a small and variable outward current (mean 7 pA). This current was observed in both tyrosine hydroxylase-immunoreactive and other bulbospinal neurons and was blocked by SKF 86466. Excitatory postsynaptic currents (EPSCs) evoked by focal electrical stimulation were isolated by incubation with gabazine and strychnine, and inhibitory postsynaptic currents (IPSCs) were isolated with 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Moxonidine reduced the amplitude of the evoked EPSCs (EC 50 ϭ 1 M; 53% inhibition at 10 M) but not their decay time constant (5.6 ms). The effect of moxonidine on EPSCs persisted in barium (300 M) and was reduced ϳ80% by SKF 86466. Moxonidine also reduced the amplitude of evoked IPSCs by 63%. In conclusion, moxonidine inhibits putative RVL presympathetic neurons both presynaptically and postsynaptically. All observed effects in the present study are consistent with an ␣2-AR agonist activity of moxonidine. I N T R O D U C T I O NCentrally acting antihypertensive drugs with an imidazoline structure, like clonidine and moxonidine, are effective in treating moderate to severe forms of hypertension (Armah et al. 1988;Prichard et al. 1997;Schafer et al. 1995;Ziegler et al. 1996). There is general agreement that a major site of action of these drugs is within the rostral ventrolateral medulla (RVL) (Punnen et al. 1987; reviewed by Reis 1996), but their specific neuronal targets are unknown. The RVL is critical for sympathetic tone generation and blood pressure control because it contains bulbospinal neurons (presympathetic neurons) that contribute the major excitatory drive to sympathetic vasoconstrictor and cardiac preganglionic neurons (McAllen et al. 1997;Sun 1995). The presympathetic neurons include a catecholaminergic cell group (C1 cells) that express the A subtype of ␣2-ARs (Guyenet et al. 1994). Activation of ␣2-ARs by norepinephrine (NE) in RVL bulbospinal neurons in vitro (C1 cells and others) acti...

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“…One plausible explanation for such data is that there is network activity or at least coordination between the two pre-motor cell groups in the same way as occurs in the respiratory system. However, there are other explanationsincluding the possibility that C1 neurons are indeed auto-active in some circumstances (Kangrga & Loewy 1995;, or that RVLM neurons simply act to integrate central and peripheral inputs without requiring intrinsic mechanisms to maintain activity. Clearly, much more work is needed to understand the extent to which these different possibilities are important parts of the whole (Lipski et al 2002).…”

Section: (D) Motor Pathwaysmentioning

confidence: 99%

Differential regulation of the central neural cardiorespiratory system by metabotropic neurotransmitters

Pilowsky

Lung

Spirovski

et al. 2009

Phil. Trans. R. Soc. B

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Central neurons in the brainstem and spinal cord are essential for the maintenance of sympathetic tone, the integration of responses to the activation of reflexes and central commands, and the generation of an appropriate respiratory motor output. Here, we will discuss work that aims to understand the role that metabotropic neurotransmitter systems play in central cardiorespiratory mechanisms. It is well known that blockade of glutamatergic, gamma-aminobutyric acidergic and glycinergic pathways causes major or even complete disruption of cardiorespiratory systems, whereas antagonism of other neurotransmitter systems barely affects circulation or ventilation. Despite the lack of an 'all-or-none' role for metabotropic neurotransmitters, they are nevertheless significant in modulating the effects of central command and peripheral adaptive reflexes. Finally, we propose that a likely explanation for the plethora of neurotransmitters and their receptors on cardiorespiratory neurons is to enable differential regulation of outputs in response to reflex inputs, while at the same time maintaining a tonic level of sympathetic activity that supports those organs that significantly autoregulate their blood supply, such as the heart, brain, retina and kidney. Such an explanation of the data now available enables the generation of many new testable hypotheses.

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Whole-cell recordings from visualized C1 adrenergic bulbospinal neurons: ionic mechanisms underlying vasomotor tone

Cited by 63 publications

References 52 publications

Rhythmic Properties of Neurons in the Rostral Ventrolateral Medulla of the Rat In Vitro: Effects of Clonidine

Rhythmic Properties of Neurons in the Rostral Ventrolateral Medulla of the Rat In Vitro: Effects of Clonidine

Prototypical Imidazoline-1 Receptor Ligand Moxonidine Activates Alpha2-Adrenoceptors in Bulbospinal Neurons of the RVL

Differential regulation of the central neural cardiorespiratory system by metabotropic neurotransmitters

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